E: The repository 'https://deb.debian.org/debian bullseye-bpo Release' does not have a Release file.
N: Updating from such a repository can't be done securely, and is therefore disabled by default.
N: See apt-secure(8) manpage for repository creation and user configuration details.
It looks like it should be bullseye-backports instead of bullseye-bpo; making that change gets it working for me.
https://haproxy.debian.net/#?distribution=Debian&release=bullseye&version=2.4 tells me to add the source
deb http://deb.debian.org/debian bullseye-bpo main
-- but when I runapt update
it fails with:It looks like it should be
bullseye-backports
instead ofbullseye-bpo
; making that change gets it working for me.